Empire State Bldg and Twin Towers were hit by planes but only the Towers Fell; Why? July 28, 2009

 

On This Date In History: At about 9:49 AM on July 28, 1945 a B-25 Mitchell hit the 79th floor of the world’s then tallest building, the Empire State Building.  Two crew members and a passenger were killed in the bomber and 11 people in the building were killed as well. The building was largely empty because the accident happened on a Saturday. 

Now, why did this building not collapse like the Twin Towers? 

Hole left by B-25

Model of Empire State Bldg Superstructure

 First off, the B-25 was a relatively small plane by today’s standards.  It was also not full of fuel.  The 767′s flown into the World Trade center weighed about 10 times that of the B-25 and was flying about 4 times faster.  The chart at the left shows that the kinetic energy of a fully loaded 767 at impact was about 160 times that of the B-25.  I have linked below to the article that goes with the chart as well as an accompanying article writer with Aerospaceweb used numbers that concluded the energy was 60 to 100 times greater. 

The Twin Towers were built with a superstructure unlike any other.  The main support system was internal with the outer skin actually acting as part of the support structure.  The Empire State Building is built in a more traditional honeycomb type system.  When the B-25 hit, much of the energy was absorbed by the outer walls whereas the Twin Towers not only had the destruction of the outer skin compromise the integrity, but the

WTC Support Derived from Center Support and Outer Skin

energy went all the way through to the main interior structure.  Many engineers found it amazing that the building was still standing at all.  The impact dislodged much of the heat protecting insulation on the steel in the support structure of the World Trade Center and so the voluminous amounts of hot jet fuel eventually weakened the floor supports, causing a collapsing pancake effect of the floors which resulted in catastrophic failure of the entire structural integrity.  Similar incidents with very dissimilar details and results.  Here is the complete story from Aerospaceweb which outlines the incident in 1945 and makes a detailed comparisons.

Why Empire State Building Did Not Collapse After Being Struck By B-25 Compared with WTC

Explainer About Differences in WTC and Empire State Building with Commentary & Graph

Wednesday Evening

Weather Bottom Line:  With the clouds so prevalent today, I suspect it will be very difficult for us to hit 90 and this was the last slight chance to do so for the rest of the month.  So,  without the unexpected happening, it appears that we will have the first July in Louisville recorded history without a 90 degree day and thats a tough thing to do considering that these days the official numbers are kept at the airport. 

We have a front approaching slowly.  It should be here by Wednesday evening.  Couple of things….not totally out of the realm of possibility that we get an isolated t’storm or two popping up in the heat of this afternoon.  But, the rain chances will ramp up for Wednesday.  Right now, severe weather does not appear to be too likely but there does appear to be a wave that will run along the front as it moves through.  Not totally out of the question that some stronger storms get initiated by the wave as it rolls through.  Then it appears that the front will get hung up so rain chances with numerous clouds will remain for the rest of the week.

Typhoon Hits Taiwan(again) Bomber Hits Tallest Building July 28, 2008

Look for a hot day with reasonable humidity, though probably not as palatable as Sunday.  A warm front will begin to lift north and as it does, a little disturbance may move down that would provide the opportunity for a few t’storms in the afternoon.  Tuesday will be hot and humid  with isolated t’storms and the same is true on Wednesday, though the storms may be more numerous with a frontal system approaching.

Typhoon Fung Wong struck Taiwan early Monday with winds in the 105 to 115 mile per hour range. There will probably be flooding and stories of destruction.  This is interesting…the first story linked below is the AP story as the storm made landfall.  The second is a preliminary story from a Chinese New Website talking about the storm’s predicted landfall.  It says it will hit the Northern Philippines!  My guess is that since China doesn’t officially acknowledge Taiwan, the writer is calling the island part of the Philippines.  That gives me pause because I had thought that China considered Taiwan as part of it’s territory, officially.  The Chinese writer couldn’t be THAT wrong in geography…especially if he had looked on these here pages for the Fung Wong track and forecast.  Here are the two stories:

AP-Typhoon Fung Wong makes landfall

China View: Typhoon Fung Wong Intesifies, Moves Toward Philippines 

On This Date In History: At about 9:49 AM on July 28, 1945 a B-25 Mitchell hit the 79th floor of the world’s then tallest building, the Empire State Building.  Two crew members and a passenger were killed in the bomber and 11 people in the building were killed as well. The building was largely empty because the accident happened on a Saturday. 

Now, why did this building not collapse like the Twin Towers? 

 First off, the B-25 was a relatively small plane by today’s standards.  It was also not full of fuel.  The 767′s flown into the World Trade center weighed about 10 times that of the B-25 and was flying about 4 times faster.  The chart at the left shows that the kinetic energy of a fully loaded 767 at impact was about 160 times that of the B-25.  I have linked below to the article that goes with the chart as well as an accompanying article writer with Aerospaceweb used numbers that concluded the energy was 60 to 100 times greater. 

The Twin Towers were built with a superstructure unlike any other.  The main support system was internal with the outer skin actually acting as part of the support structure.  The Empire State Building is built in a more traditional honeycomb type system.  When the B-25 hit, much of the energy was absorbed by the outer walls whereas the Twin Towers not only had the destruction of the outer skin compromise the integrity, but the energy went all the way through to the main interior structure.  Many engineers found it amazing that the building was still standing at all.  The impact dislodged much of the heat protecting insulation on the steel in the support structure of the World Trade Center and so the voluminous amounts of hot jet fuel eventually weakened the floor supports, causing a collapsing pancake effect of the floors which resulted in catastrophic failure of the entire structural integrity.  Similar incidents with very dissimilar details and results.  Here is the complete story from Aerospaceweb which outlines the incident in 1945 and makes a detailed comparisons.

Why Empire State Building Did Not Collapse After Being Struck By B-25 Compared with WTC

Explainer About Differences in WTC and Empire State Building with Commentary & Graph